1. Field of the Invention
The present invention relates to a method for manufacturing a microstructure, and, in particular, to a method for manufacturing a microstructure by electrolytic plating of a metal with use of a mold, especially a microstructure having a high aspect ratio.
2. Description of the Related Art
A micro fine structure having periodic structure, especially a high aspect ratio structure is needed in a large number of fields. For example, the X-ray absorption characteristic of a microstructure composed of gold is utilized in a nondestructive test of an object as an industrial application, and also utilized in, for example, radiography as a medical application. A microstructure in these applications forms a contrast image by utilizing an absorption difference in X-ray transmission depending on constituent elements and a density variation in an object or a biological object, and is called the X-ray absorption contrast method.
Further, the phase contrast method using a phase difference of X-ray has been researched actively since even light elements can be imaged by this method, and for example, the propagation method and the Talbot interference method has been becoming feasible in principle. Generally, the method using Talbot interference is carried out with use of an absorption grating comprised of gold having a periodic structure and large absorption of X-ray. Since it is difficult to directly manufacture a golden microstructure having a high aspect ratio (“aspect ratio” is defined as a ratio of a height or depth h and a width w of a structure (h/w)), the method of filling a mold with gold by plating is preferable as a method for manufacturing a golden absorption grating constituted by a periodic structure.
Japanese Patent Application Laid-Open No. 2007-203066 discusses a structure of an X-ray optical transmission grating for the above-described phase contrast method. Further, with the aim of solving the problem of a significant reduction in fabrication precision according to an increase in the aspect ratio of a structure, Japanese Patent Application Laid-Open No. 2007-203066 discusses a combination of partial gratings which functions as one grating.
However, Japanese Patent Application Laid-Open No. 2007-203066 does not discuss a method for manufacturing a microstructure having a high aspect ratio.